http client: Only read response body if response code < 400.

The jdk http client will not allow reading the body if the response code >= 400.

Relates to elastic/elasticsearch#271

Original commit: elastic/x-pack-elasticsearch@08836f92ae

src/main/java/org/elasticsearch/watcher/input/http/ExecutableHttpInput.java

@@ -42,8 +42,10 @@ public class ExecutableHttpInput extends ExecutableInput<HttpInput, HttpInput.Re
         HttpRequest request = input.getRequest().render(templateEngine, model);
 
         HttpResponse response = client.execute(request);
-        Payload payload;
-        if (input.getExtractKeys() != null) {
+        final Payload payload;
+        if (!response.hasContent()) {
+             payload = Payload.EMPTY;
+        } else if (input.getExtractKeys() != null) {
             XContentParser parser = XContentHelper.createParser(response.body());
             Map<String, Object> filteredKeys = XContentFilterKeysUtils.filterMapOrdered(input.getExtractKeys(), parser);
             payload = new Payload.Simple(filteredKeys);

src/main/java/org/elasticsearch/watcher/support/http/HttpClient.java

@@ -112,10 +112,15 @@ public class HttpClient extends AbstractComponent {
         }
         urlConnection.connect();
 
-        byte[] body = Streams.copyToByteArray(urlConnection.getInputStream());
-
-        HttpResponse response = new HttpResponse(urlConnection.getResponseCode(), body);
-        logger.debug("http status code [{}]", response.status());
+        final HttpResponse response;
+        final int statusCode = urlConnection.getResponseCode();
+        logger.debug("http status code [{}]", statusCode);
+        if (statusCode < 400) {
+            byte[] body = Streams.copyToByteArray(urlConnection.getInputStream());
+            response = new HttpResponse(statusCode, body);
+        } else {
+            response = new HttpResponse(statusCode);
+        }
         return response;
     }
 

src/main/java/org/elasticsearch/watcher/support/http/HttpResponse.java

@@ -24,7 +24,7 @@ public class HttpResponse implements ToXContent {
     private final BytesReference body;
 
     public HttpResponse(int status) {
-        this(status, BytesArray.EMPTY);
+        this(status, (BytesReference) null);
     }
 
     public HttpResponse(int status, String body) {
@@ -44,6 +44,10 @@ public class HttpResponse implements ToXContent {
         return status;
     }
 
+    public boolean hasContent() {
+        return body != null;
+    }
+
     public BytesReference body() {
         return body;
     }
@@ -69,10 +73,12 @@ public class HttpResponse implements ToXContent {
 
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-        return builder.startObject()
-                .field(STATUS_FIELD.getPreferredName(), status)
-                .field(BODY_FIELD.getPreferredName(), body.toUtf8())
-                .endObject();
+        builder = builder.startObject().field(STATUS_FIELD.getPreferredName(), status);
+        if (hasContent()) {
+            builder = builder.field(BODY_FIELD.getPreferredName(), body.toUtf8());
+        }
+        builder.endObject();
+        return builder;
     }
 
     public static HttpResponse parse(XContentParser parser) throws IOException {
@@ -108,12 +114,11 @@ public class HttpResponse implements ToXContent {
         if (status < 0) {
             throw new ParseException("could not parse http response. missing [status] numeric field holding the response's http status code");
         }
-
         if (body == null) {
-            throw new ParseException("could not parse http response. missing [status] string field holding the response's body");
+            return new HttpResponse(status);
+        } else {
+            return new HttpResponse(status, body);
         }
-
-        return new HttpResponse(status, body);
     }
 
     public static class ParseException extends WatcherException {

src/test/java/org/elasticsearch/watcher/support/http/HttpClientTest.java

@@ -29,6 +29,7 @@ import java.nio.file.Paths;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.nullValue;
+import static org.hamcrest.core.Is.is;
 
 /**
  */
@@ -154,4 +155,19 @@ public class HttpClientTest extends ElasticsearchTestCase {
         assertThat(recordedRequest.getBody().readUtf8Line(), equalTo("body"));
     }
 
+    @Test
+    public void test400Code() throws Exception {
+        webServer.enqueue(new MockResponse().setResponseCode(400));
+        HttpRequest.Builder request = HttpRequest.builder("localhost", webPort)
+                .method(HttpMethod.POST)
+                .path("/test")
+                .auth(new BasicAuth("user", "pass".toCharArray()))
+                .body("body");
+        HttpResponse response = httpClient.execute(request.build());
+        assertThat(response.status(), equalTo(400));
+        assertThat(response.hasContent(), is(false));
+        assertThat(response.body(), nullValue());
+    }
+
+
 }